The present invention relates to object identification systems and in particular to an improved label for use in such systems wherein the coding on the label is adapted to vary in response to a change in conditions to which the object being identified is subjected or within the object.
In U.S. Pat. No. 3,225,177 which is commonly assigned with the present application, a system for the automatic identification of objects is disclosed. The commercial form of the invention is marketed under the trade name KARTRAK by the Servo Corporation of America of Hicksville, N.Y. The KARTRAK system is the American Association of Railroads approved form of railroad car identification and, accordingly, virtually every freight car in the United States is furnished with a KARTRAK label.
The label comprises a plurality of stripes formed of retroreflective material arranged in a two-position, base four code. At various sites, such as freight yards, terminals, etc. scanners are provided which, in effect, "read" the labels to decipher alpha-numeric data identifying the cars. In this manner, automated surveillance can be maintaind of the millions of railroad cars across the country.
The KARTRAK labels comprise a vertical array of modules of parallel, horizontal stripes, each module having two horizontal stripes. The fields are colored blue, orange, or black (the absence of blue or orange) and white (the presence of both blue and orange). The modules are coded to contain information as to the car identification number, carrier identification code and equipment code as well as control modules which generate a start signal, a stop signal, and parity check code. The standard KARTRAK label contains 13 color coded modules.
In addition to their use on railroad cars, the KARTRAK labels are also used on containers, truck trailers and the like. Indeed, such color coded labels can be and are used in many other types of object identification systems. One of the principal advantages of the KARTRAK and similar systems is that the object may be moving while its label is being scanned and decoded.
Oftentimes, the environment within or about an object to which a label is affixed is critical. A dramatic example of this is the common refrigerator car where it is essential that the temperature within the car be maintained below a certain temperature. To this end, the car is equipped with the necessary refrigeration equipment. Similarly, there are other cars wherein the temperature must be maintained above a certain temperature; wherein the pressure must be maintained above or below certain critical values; wherein the container must be maintained airtight or constant air circulation must be maintained, etc.
The principal object of the present invention is to provide an improved label of the type discussed above which not only contains basic identification information but additionally provides constant monitoring of the object and generates a signal to an associated scanning station indicative of an abnormal condition within or associated with the object. A further object is to provide such a system which is compatible with the existing KARTRAK system and equipment.